Means for electrically baking out coils



Dec. 27, 1955 B. s. LIGHTFOOT 2,728,843

MEANS FOR ELECTRICALLY BAKING OUT COILS Filed July 11, 1952 o 24 e a}. o6 i PLJJ INVENTOR Byro nflzzyhfoaz" 7 BY MQ W ATTORNEYS United StatesPatent'O MEANS FOR ELECTRICALLY BAKING OUT COILS Byron StricklandLightfoot, Cleburne, Tex., assignor of one-half to Elizabeth Craps,Cleburne, Tex.

Application July 11, 1952, Serial No. 298,236 3 Claims. (Cl. 219-20)This invention relates to an improved means for electrically baking outcoils.

An object of this invention is to provide an improved means for bakingout the coils in electrical appliances, such as for example the coils ofmotors, transformers, or other electrical appliances, wherein thearticles have been dipped in industrial varnish. In the past the coilshave been baked out by placing the same in ovens or other heatedchambers, but this process is relatively slow because where the coil isrelatively heavy or compact, the inner convolutions take longer to dryout than the outer convolutions.

Another object of this invention is to provide an improved means forbaking out dipped coils wherein the entire coil is subjected to the sameheat, and the drying means is controlled by a thermostat so that thecoil will not be over-heated or burned during the baking process.

A further object of this invention is to provide a baking means which issimple in construction and portable so that the device can be hooked upwith any convenient electrical outlet.

With the above and other objects in view, my invention consists in thearrangement, combination and details of construction disclosed in thedrawings and specification, and then more particularly pointed out inthe appended claims.

In the drawing- Figure 1 is a perspective view of a coil baking meansconstructed according to an embodiment of this invention, showing thedevice in operative position with respect to a coil,

Figure 2 is a diagrammatic view showing the electric circuits embodiedin this invention.

Referring to the drawing, the numeral designates generally a coil whichis preferably of the resistance type, and one end of the coil 10 has aconductor 11 connected therewith. The other end of the coil 10 has aconductor 12 connected therewith and conductor 12 is connected to apower line 13. A second power line 14 is connected to one side of athermostat 15 which is of the normal circuit closing type, and conductor11 is also connected to the other side of the thermostat 15.

An ammeter 16 is interposed in conductor 14 and is adapted to registerthe amperage of current passing through the coil 10. A pilot light 17 isconnected across conductors 11 and 13. Coil 10 has a plurality ofconductors 13 connected to tapped convolutions of the coil andconductors 18 are connected to contact points 19 of a regulating tapswitch 20. The regulating tap switch 29 includes a movable contact arm21 which has one end of a conductor 22 connected therewith. Conductor 13is connected to a contact point 23 carried by switch 20, and a conductor24 is connected with contact 23. The two conductors 22 and 24, as shownin Figure l, have clips 25 secured to the opposite ends thereof so thatconductors 22 and 24 may be connected with the ends 26 and 27 of a coil28, which is to be dried.

The apparatus hereinbefore described is mounted in a cabinet 29 withammeter 16 disposed on the front panel 30 of the cabinet, and the knob31 for switch arm 21 being disposed below the meter 16 and projectingfrom the front panel 30.

In the use and operation of this baking means, the dipped coil 28 isconnected with the switch 20 by connecting the ends of the coil withclips 25. The thermostat 15 is preferably disposed interiorly of thecoil 28 so that when a current is passing through the coil 28 and thelatter is being heated by this current, thermostat 15 will regulate theamount of heat to be applied to the coil. In other words, thermostat 15,which is normally closed, will upon heating of the coil 28 to apredetermined degree break the electric circuit to the coil 28 so thatthe latter will not be burned or over-heated. Switch arm 21 is adjustedso as to apply the desired even heat to the coil 28 so that there willnot be any greater current applied to the coil 28 than the coil was madeto stand.

When the conductors 13 and 14 are connected with a source of currentsupply, pilot light 17 will initially be lighted by reason of theinitial closing of the thermostat switch 15. In the event the coil 28should be heated to a point where the thermostat will break the electriccircuit thereto, pilot light 17 will go out so that a glance at thepanel 30, within which pilot light 17 is mounted, will indicate whetherthe heat is still being applied to coil 28.

With a baking apparatus as hereinbeiore described. the coil 28 will bakeevenly from the inside to the outside and the baking out process can beperformed in a shorter time than has heretofore been possible where thecoil is placed in an oven or other heated chamber. The device can beused for baking coils such as the stators or rotors of motors, or thecoils of transformers or other electrical appliances. The apparatushereinbefore described is compact in assembly and readily portable sothat the device can be connected with any suitable electrical outletwhich may be convenient.

I do not mean to confine myself to the exact details of constructionherein disclosed, but claim all variations falling within the purview ofthe appended claims.

What I claim is:

1. A varnish covered coil and means for baking out in open air saidcoil, said means comprising a resistance coil, a pair of supplyconductors connected to the ends of said resistance coil, a selectorswitch formed of a plurality of fixed contacts and a movable contact,conductors connecting said contacts with spaced convolutions of saidresistane coil, a conductor connected at one end with the other of saidsupply conductors and connected at the other end with one end of saidvarnish covered coil, and a conductor connected at one end with saidmovable contact and connected at the other end to said varnish coveredcoil.

2. A varnish covered coil and means for baking out in open air saidcoil, said means comprising a resistance coil, a pair of supplyconductors connected to the ends of said resistance coil, a selectorswitch formed of a plurality of fixed contacts and a movable contact,conductors connecting said contacts with spaced convolutions of saidresistance coil, a normally closed thermostatic switch interposed in oneof said supply conductors and engaged with said varnish covered coil, apilot light connected across said supply conductors, a con- .ductorconnected at one end with the other of said supply conductors andconnected at the other end with one end of said varnish covered coil,and a conductor connected at one end with said movable contact andconnected at the other end to said varnish covered coil.

3. A varnish covered coil and means for baking out in open air saidcoil, said means comprising a resistance coil, a pair of supplyconductors connected to the ends of said resistance coil, a selectorswitch formed of a plurality of fixed contacts and a movable contact,conductcrs connecting said contacts with spaced convolutions of saidresistance coil, a normally closed thermostatic switch interposed in oneof said supply conductors and engaged with said varnish covered coil, anamrneter interposed in said one supply conductor, a conductor connectedat one end with the other of said supply conductors and connected at theother end with one end of said varnish covered coil, and a conductorconnected at one end with said movable contact and connected at theother end to said varnish covered coil.

References Cited in the file of this patent UNITED STATES PATENTS DevineJune 20, 1922 Glitzke June 7, 1932 Maize Mar. 25, 1941 Crawford Apr. 29,1941 Maize Dec. 9, 1941 Koch Ian. 4, 1944 Youhouse Nov. 2, 1948 AckleyMar. 14, 1950

